Electric discharge device



Oct 2-6, 1948. P. L.. SPENCER 2,452,077

A ELECTRIC DISCHARGE DEVICE lFiled Jan. 19, 1944 l 2 sheets-sne'et 1 A v.al

N l L yml;

Oct. 26, 1948. F L. SPENCER ELECTRIC DISCHARGE DEVICE Filed Jan. ,19,1944 2 Sheets-Sheet 2 Patented ct. 26, i948 ELECTRIC DISCHARGE DEVCPercy L.' Spencer, West Newton, Mass., assigner to RaytheonManufacturing Company, Newton, Mass., a corporation of Delaware fApplication January 19, 1944, Serial No. 519,077

This invention relates to a magnetron oscillator Vwhich is adapted togenerate oscillations of hyper frequency and having Wave lengths of theorder of a few centimeters or less. Heretoiore such oscillators haverequired a relatively complex anode configuration which was difficult toconstruct accurately and which tended to produce spurious oscillations,thus decreasing the eiliciency of the oscillator.

An object of this invention is to devise a magnetron having an anode ofsimple construction wherein the frequency of oscillationfis xed by asimple and easily constructed configuration.

Another object is to provide a magnetron of the above type in which theoscillations are proguide;

Fig. 2 is a cross-section taken along line 2-2 of Fig. 1;

Iig. 3 is a diagrammatic perspective View broken away to show analternative mode of coupling the tube of Fig. 1 to a wave guide;

Fig. 4 is a cross-section of another embodiment of the invention whereina plurality of oscillating slots are utilized;

Fig. 5 is a cross-section taken along 5-5 of Fig. 4; and f Fig. 6 is afragmentary section similar to Fig. 4 showing an alternative mode ofcoupling to awave guide.

v A The magnetron illustrated in Figs. 1 and 2` comprises a cylindricalanode I of suitable conducting material, such as copper, and a centrallylocated lamentary cathode 2 of the thermionic type. 'Ihe anode andcathode are contained within a highly evacuated glass envelope 3containing a reentrant stem V4. The anode I is supported by a conductingstandard 5 sealedin the stem 4 and provided with a lead-in conductor Ewhich is sealed through said stem and provides an external electricalconnection for the anode.

.The cathode 2 is supported Iby a pair of con- 40mm. (o1. 25o-27.5)

ducting standards l, likewise sealed in the stem Il and each providedwith a lead-in conductor 8 sealed through said stem in order to provideexternal electrical connections to the cathode. The cathode 2 may beprovided with heating current through leads 8 so as to raise it to atemperature of thermionie emission. Light metal shields 9 may beprovided at opposite ends of the electrode structure so as to preventelectrons from being projected throughA the lends of the anode I towardthe glass walls of the envelope 3. These shields may be convenientlysupported from the cathode standards 1. Magnet poles I0 and I I areprovided in order to create a magnetic eld extending axially along theanode cylinder l and substantially parallel with the lamentary cathode2. The anode I is provided with anv elongated slot I2 cut through thewall of said anode in a direction substantially parallel with the axisof the anode cylinder. The slot I2 is narrow as compared with itslength. Also its length is selected so as to be substantially onehalfthe Wave length of the oscillations which the magnetron is adapted togenerate.

When in the arrangement as described above the cathode is heated totemperature of thermionic emission, a suitable Voltage is impressedbetween the cathode and the anode, and the magnetic field is of theproper value, oscillations will be generated in the anode cylinder Iaround the slot I2. These oscillations will have a wave length which issubstantially twice the length of the slot I2.

I believe that the operation of the device is substantially as follows.The magnetic iield set up about the cathode 2 causes the electrons,which are emitted from said cathode and accelerated by the anodevoltage, to travel in orbital paths around the cathode 2. Thus in thevicinity of the slot l-2 electrons tend to travel past said slot in adirection normal to its length and induce varying electric charges onopposite sides of said slot. This tends to set up oscillations aroundthe slot at a frequency at which the slot is resonant. The voltages setup across the slot react on the electrons passing the slot and tend tobunch these electrons in such a way that pulses of electronsperiodically pass theV slot with such periodicity and phase as toreinforce the abovementioned oscillations. As a result strongoscillations are generated. which tend to radiate hlyper frequencyenergy from the vicinity of said s ot. I

The energy radiated from the slot I2 may be guided in a desired mannerby inserting that portion of the anode containing said slot into a waveguide I3. For example, the wave guide I3 may be provided with an openingM in one side thereof, and the upper end of the envelope 3 may loeinserted through said opening I4 so that the slot I2 lies transverse tothe wave guide I3. Under these conditions I believe that the energy coming' from ithe slot. i 2 tends to .exciterthe zwave guide I-3inalso-cal1edtransverse magnetic mode in which the magnetic vectors aretransverse to the wave guide and the electric Vectors within the Waveguide are substantially paralleLtothedirection in which energy ispropagatedthrough the Wave guide. The wave guideet redesigned, to haveproper dimensions fompropagatingzzthercscillations generated by themagnetron and `is closed at one end by a conducting. surface .I5

`mayoccur. 'iPoles 23 ,.andiZd, 1 of: a 4lsuitably enerspaced the properdistancefrom the 'slot`i2 all in accordance with well known waveguideprin'-y ciples. Under these conditions the energy gen- ,eratedwby.the -magnetron willi loe .propagated @through thewave .guide i.3;in.the,-directicn of :thearrow P assshowninf-Fig; 2.

`(Instead Aof. coi 1.1: ling A.th-e.magnetron tor-a wave vz; guidesasdescribed .aboveg various other coupling :arrangements ymay ,be devised.@For-example, ,las :,sllownfin 3, Lthe; magnetron may be inserted rnetonnet, end of. afrectangular waveguide l. IY3 with the, axisof .theanode Ac :ylind-er,l i substantially par allel-'withxthelonga'dimensionof :the cross-section L ofsrsaidwavagude. .Like-wisethe,lslot-l2 lwill he .'parallelttotsaidz'longt dimension. f Underthesecon- ',ditions energyiradiatedffrom the=slot l'-lwillbe ,lpropagated-.along l the wave jguideni 3. I believe -thatzin thiscasethelenergy .isf propagated in a so- ;l

.-called.transversefelectricv mode `linzwhich.theelectrickvectorsextendk across .the narrow vdimension I "',Qffztherectangular-,wave guide A 13..'.andethe -magnetic :vectors :extendsubstantially i parallel -to f the direction ogpropagatlcn tofwtheenergy. through Y:th'ewaye guide.

@In tmest i instances it; mayI be tdesired .-.tozutilze L. a plurality,ofioscillatingi slots instead: of:.asingle slot, as shownrin Figa-1113.Such; ayplural :slot :arrangement mayi taker-the `form aeg-shown; inFigs. .4 fand-1A 5 .Thisiemhodiment comprises aghollow :cathode::sleevefil r,within :which-uis rrcontairreel.7 a :heater lament I-'LnSurroundingithexcathcdepl y is an; anode gcylindernliormedepf.isuitably,con

ducting, material, kSui-1h as, copper. *,TI-helanodacyl-`findemS;,Dr,ovided with-aiplurality'pf slots dit eachsimilar-atoth'eeslotf` |22 ,tassdescribedlin;connection with Figs. l and2. As indicated, :leach: ofzithe :slots .I 9; should., halles.atlengthlzsubstantallyaequal -.t c onehaifmf ',thefwave lengthofitheioscillations `to,virrey.generated. Y--Plllhenf aimagnetic ieldfis :set Mllpvlarallel .tok .ftheK axis: ofrfthe *.pcathoderl E as willbeedescribed- :be-low, oscillations are generated :aboutteach .ofatheislots 19. .Slrrorderto teedrtliesetoscillations.;intoyascomrnonlzoutput, Aaa.; common i a fpair sofpoleepieces :2 Mandi 22 'aref'.hermeticall-y gized electromagnet or of.a ypermanent magnet,

are placed in contact with the pole pieces 2| and respectively.

. 4Thecathode cylinder I6 comprises 4a tubular conducting sleeve coatedwith the usual electron emittingzoxides.z.0ne end of the heater I1within .fsaidzsleeveis;electrically connected to the top 'closed,endthereof, The sleeve I6 is formed with a ,lower reduced tubular end 25which passes through an opening 26 formed in the pole piece 2|. The.lower end of the reduced tubular section 25 fits into a recess in theupper end of a con- Nducting rod- 21 provided-.With-.a.borefaZBi'through which `an ,insulated ,wire 29 connected ,to-fthe lowerrend-.ofthe heater II passes. `A'Ihelowerj end of said insulated .wire 29 passesout throughva lglass `seal l30 carried from the lower end .Oi-lthe yrod21 byian'zintermediate-sealingvsfleeveI. Surrounding the rod 21T-isatubular ;metal.1shell,.32, the upper'fend of lwhichisfinserteddntoffanenlarged end of the openingsl.:ofthepolejpiece vI andhermeticallyljoined;therewithasfbyfbrazing. Tothe .lower endet.the-fshell-w32 lisfisealed .a glass tube-3,3,vthe lower,endfof-which isin turn sealed to arnetalfsealingqup hermeticalglyifastened totheextelior.- oith'eirod 21. .'Theconductor A2.11 serves lasy anexternalfelectr-ical; .connectionto the heater l'Lwhile the cup .34:serves asian external electrical connection to .zthef-cathodes1eeve,as,well .as to theupperrendof saidzheater. Suitableelectricalfconnectionfcan-,be made tothe anode cylinder f. I8.atanyypointontthe ring f 2'0sor at any of theconductingeeiements.i-connected thereto.

zIn- .order to;lead,.theenergyifromi(theswavegguide 281110asuitableutilizationvdevice, .ag-coupling loop -35 t-isxinterposed:inuthe space: withinfsaiid :wave

guide with the axis of said loop interceptedabyithe :magnetici-eid'.'withinfsaidswave guide. .One -end Y,of i; the-.coupling 'loopc:fis-:electrically :connected -top-thetinnerendrofralpipesihermeticallynsealed through a wall of the ring 20. The outer '.endiofsaid couplingdoopzf is..connested-3fty` a conductor 31 which passesthrough said pipe 36 and extends yithrlough;aaglass; sea1e38lcarried: atthe outerfen y.of saidpipe. l

When :the-devicaas describedaboveissinioperation,=.ith'e .oscillationenergy generated around each slot .i Suisifedlintoftherwaveguide20twlierein it is propagated to the lcouplingloopf and con- ,ductecl'romfsthecstructure'i'byrzthe concentric' line arrangement associatedwith said coup1ing`loop. In:order:forftheloperation tolproeeed wthmaxibespaced from each other around the-anodecyl- Linder I8 loyaal-distance:substantiallylequal toone- Ahalf ofi-the i wave lengthl oi theyoscillations lwithin Vythe;wavenguide 20. iilfbelievethatfunder-theabove conditions the slots 21'91exciteJ-the-wave x guidef'lZfD @ther.means fofifcoupling the oscillator-y Lenergy within'thewave:guidef toanlexternalewaveguide may-be'; utilized. Y VFlorexample;- as showninlFig-.l-, ai hollow iwan/el guideYSQ `runway-'be'- connectedtotheexterior of the ring 20 and coupled to the interior of said ring by acoupling iris opening 40. It is to be understood that the wave guide 39is hermetically sealed 01T at its outer end in a, suitable manner, suchas shown for example in the copending application of William C. Brown,Serial No. 506,608, led October 16, 1943.

I have found that devices constructed in accordance with the foregoingprinciples can be made accurately with a minimum of diiliculty. Further,such devices tend to oscillate at the desired output frequency and areremarkably free from tendencies to generate spurious oscillations whichmight tend to decrease the efciency thereof.

Of course it is to be understood that this invention is not limited tothe particular details as described above as many equivalents willsuggest themselves to those skilled in the art.

What is claimed is:

1. A magnetron comprising: a cathode; an an ode surrounding saidcathode; and means adjacent said cathode and said anode for establishinga magnetic eld in a direction transverse to the path therebetween; saidanode having a plurality of perimetrically closed slots formed thereinand spaced from each other around said anode by a distance substantiallyequal to the length of a half-Wave at the frequency desired of theoutput of said magnetron; each of said slots being of a lengthsubstantially equal to a half-wave length in a direction parallel tothat of said magnetic field.

2. A magnetron comprising: a cathode; an anode surrounding saidcathodeiand means adjacent said cathode and said anode for establishinga magnetic iield in a direction transverse to the path therebetween;said anode including a toroidal cavity resonator, the inner wall ofwhich is provided with a plurality of perimetrically closed slots spacedfrom each other around said wall by a distance substantially equal tothe length of a half-wave at the frequency desired of the output of saidmagnetron; each of said slots being of a length substantially equal to ahalfwave length in a direction parallel to that of said magnetic field.

3. A magnetron comprising: a cathode; an open-ended anode surroundingsaid cathode; and a pair of pole pieces sealed, respectively, to theopen ends of said anode for establishing a mag- .netic field in adirection transverse to the path between said cathode and said anode;said anode having a plurality of perimetrcally closed slots formedtherein and spaced from each other around said anode by a distancesubstantially equal to the length of a half-wave at the frequencydesired of the output of said magnetron; each of said slots being of alength substantially equal to a half-wave length in a direction parallelto that of said magnetic eld.

4. A magnetron comprising: a cathode; an open-ended anode surroundingsaid cathode; and a pair of pole pieces sealed, respectively, to theopen ends of said anode for establishing a magnetic eld in a directiontransverse to the path between said cathode and said anode; said anodeincluding a toroidal cavity resonator the inner wall of which isprovided with a plurality of perimetrically close-d slots spaced fromeach other around said wall by a distance substantially equal to thelength of a half-wave at the frequency `desired of the output of saidmagnetron; each of said slots being of a length substantially equal to ahalf-wave length in a -direction parallel to that of said magneticfield.

PERCY L. SPENCER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,523,776 Hull Jan. 20, 19252,063,342 Samuel Dec. 8, 1936 2,084,867 Prinz et al June 22, 19372,129,713 Southworth Sept. 13, 1938 2,154,758 Dallenbach Apr. 18, 19392,241,976 Blewett et al May 13, 1941 2,247,077 Blewett June 24, 19412,250,698 Berline July 29, 1941 2,284,751 Linder June 2, 1942 2,295,315Wolff Sept, 8, 1942 2,348,986 Linder May 16, 1944 FOREIGN PATENTS NumberCountry Date 215,600 Switzerland Oct. 16, 1941

